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Traffic Sensors – are they able (can they be made able) to detect bikes?

This topic contains 14 replies, has 8 voices, and was last updated by  Mikhail 10 mos, 1 week.

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Alicia412

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Sep 19 2013 at 12:08pm #

I’ve been wondering this for awhile and was wondering if anyone else has too. It looks like this is possible but maybe there’s not enough demand in the city? See this: http://www.humantransport.org/bicycledriving/library/signals/detection.htm. In my opinion, it would just be awesome on an already bike friendly corridor like East Liberty Blvd to have these, so I don’t have to wait for a car to pull up so I can turn left. Much better than resorting to running the red like I have been tempted to in the past…


Swalfoort

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Sep 19 2013 at 12:16pm #

Yes. Such sensors exist. But, more specialized means more expensive, so rarely employed in PA.


jonawebb

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Sep 19 2013 at 12:20pm #

I don’t usually have a problem with getting the traffic sensors to operate. I just follow the instructions from the PA Bicycle Driver’s Manual (which I highly recommend, BTW):
“Recognize the detector by a square or octagonal pattern of thin lines in the pavement, where slots were cut for the detecting wires. The detector is most sensitive if you ride along one of the wires.”
But I agree, it makes sense for us to get the kind of traffic light signals that can detect bicycles. As the manual says: “Detectors are made that work for bicycles, at little or no additional cost. Federal design guidelines exist for these detectors. If you put enough pressure on your local and state government, bicyclists can avoid the crashes and the city can avoid the lawsuits which may follow.”


edmonds59

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Sep 19 2013 at 12:33pm #

There is a pavement sensor on my commute home, when I’m almost there, that I have never been able to trip, even using the prescribed method. And it is a light that allows me to cross Rt 60/Steuby Pike, so it’s a big deal.
I will wait a few minutes to see if it turns, if it doesn’t, I wait until it’s safe and blow it. If it doesn’t detect me and switch, I consider it a malfunctioning device, which makes it me-legal.


Swalfoort

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Sep 19 2013 at 12:51pm #

That’s the process….

Many don’t even work for my scooter.

Some detect metal, others can be triggered by vibration or something.

We need sensors useful for all users.


jonawebb

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Sep 19 2013 at 12:56pm #

@edmonds et al., there’s an adjustment they can make. See http://www.fhwa.dot.gov/publications/publicroads/08may/02.cfm. You may be able to get them to change the settings on the sensor.
“If a DOT engineer can see the sawcut of a 1.8- by 1.8-meter (6- by 6-foot) square or circular loop on a section of pavement, then a motorcycle or bicycle riding over the left or right edge of the loop should actuate the signal. If it does not, then (1) the loop sensitivity setting was not set for motorcycle and bicycle detection and should be raised to 6 or above, (2) the loop is malfunctioning and should be repaired (this indeed was the case for two of the loops FHWA tested), or (3) the vehicle wheel rims are not made of conductive material. The tests at both the TFHRC Intelligent Intersection and Purdue University back this conclusion. Therefore, the conclusion is true with a high degree of probability.”


salty

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Sep 19 2013 at 4:26pm #

I can get most of them to go but I defy anyone to trigger the sensor on Morewood at Forbes using a bike. I ride I big steel bike and have oriented it in every conceivable way over the sensor, leaning the frame at different angles, etc. It’s never worked, I just give up and go through it.

Larimer Ave (Southbound) @ ELB is another bad one.


StuInMcCandless

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Sep 19 2013 at 5:01pm #

McKnight at Perrymont, northbound, left-turn lane for Perrymont.
Never mind a bicycle, it does not sense my Suzuki GZ250 motorcycle. Plenty of steel there.

The operative piece of traffic law is this:

§ 3112. Traffic-control signals.

(c) Inoperable or malfunctioning signal.–If a traffic-control signal is out of operation or is not functioning properly, vehicular traffic facing a:

(2) Red or completely unlighted signal shall stop in the same manner as at a stop sign, and the right to proceed shall be subject to the rules applicable after making a stop at a stop sign as provided in section 3323 (relating to stop signs and yield signs).

In other words, once you have determined that the signal is malfunctioning (it does not detect your presence after a legal stop), you treat the corner as a four-way stop: Make sure nothing is coming, then go.


jonawebb

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Sep 19 2013 at 7:25pm #

What these guys are saying, in their study, which is based on actual tests on sensors, is: the sensor should be able to detect bicycles. If it doesn’t, it’s because it’s broken, or not adjusted right. And we should be able to do something about that, because the municipal authority responsible for the sensor employs someone who can adjust it. You just have to identify the broken sensor, talk to the right people, and get them to fix it.


Swalfoort

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Sep 19 2013 at 7:40pm #

Jon, you are correct. But cutting up pavement, recalibrating sensors, and replacing pavement takes time and money, both of which are in short supply at the local municipality level. Sounds so simple, but getting nyone to cut up a perfectly good road surface and paying to do it it tremendously difficult….


jonawebb

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Sep 19 2013 at 7:44pm #

As an engineer I doubt the design requires cutting up the pavement to change the sensitivity. I’ll bet most of them can be fixed without that.


Drewbacca

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Sep 19 2013 at 9:18pm #

I can’t think of any reason why it would require tearing up a road… the actual sensors would be at the point of power supply, what they are sensing is a change in the system caused by a passing car and not the car itself. The part buried under asphalt should be passive… any calibration would come after it is already installed (I would think).

It really just comes down to whether or not an adjustment can be made, at all.


edmonds59

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Sep 20 2013 at 5:19am #

Thanks for the ordinance link. In my circumstance, if I get some time, I will a. try and find out who the hell has jurisdiction over this particular signal (state? county? township?) and b. send them a message about getting it adjusted.
At this location, paving has been done so you can’t now see the pavement cuts. I’m hoping at some point they telegraph through again. These sensors pick up cars just fine.
Until the above thing happens, I imagine all the commuting cyclists who pass through this intersection (me) will continue to judiciously blow the light.


jonawebb

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Sep 20 2013 at 6:34am #

The report I linked to has a stencil for telling cyclists where to ride to activate the sensor. So if the municipality is especially cooperative you might be able to get them to mark it.


Mikhail

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Sep 20 2013 at 3:55pm #

jonawebb wrote:As an engineer I doubt the design requires cutting up the pavement to change the sensitivity. I’ll bet most of them can be fixed without that.

Most of sensors installed in small townships are old ones. No one would install just controller and try to connect it to old sensor. :( for the newer ones recalibrating is not necessary, just adjusting.

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